ASTM D746 covers the determination of the brittleness temperature of plastics and elastomers by impact testing. Specimens are secured to a holder, immersed in a cooled heat-transfer medium bath, and struck at a linear speed of 2000 ± 200 mm/s. After impact, specimens are examined for cracks or complete separation.
The test establishes the temperature at which 50% of specimens would probably fail under the specified conditions. Testing begins at an estimated 50% failure temperature with sets of 10 specimens, adjusting temperature in 2 or 5°C increments until the full failure transition range is identified.
This test evaluates long-term effects such as crystallization or low-temperature incompatibility of plasticizers, and is used for cable insulation and jacketing materials to predict behavior at low temperatures.